Phosphor optical element and light-emitting device using the same

ABSTRACT

A phosphor optical element includes: a base member; a phosphor-containing member that includes a transparent member containing a phosphor particle; and a cover member, wherein the base member, the phosphor-containing member, and the cover member are sequentially formed on a transparent base that is transparent to a wavelength of incident light from an excitation light source, the phosphor particle has a diameter no greater than the wavelength of the incident light, and in an arbitrary cross section of the phosphor-containing member in a direction perpendicular to a main surface of the transparent base, the phosphor-containing member has, in a direction perpendicular to the main surface of the transparent base, a thickness no greater than the wavelength of the incident light.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation application of PCT International Application No.PCT/JP2012/001661 filed on Mar. 9, 2012, designating the United Statesof America, which is based on and claims priority of Japanese PatentApplication No. 2011-177772 filed on Aug. 15, 2011. The entiredisclosures of the above-identified applications, including thespecifications, drawings and claims are incorporated herein by referencein their entirety.

FIELD

The present disclosure relates to phosphor optical elements andlight-emitting devices using the phosphor optical elements, andparticularly to a phosphor optical element in a light-emitting devicewhich is used as a light source of a projector or a light source of abacklight of a liquid crystal display device.

BACKGROUND

Recent years have seen rapid growth in a market of display devices, suchas a thin-type television and a projector. These display devices includeliquid crystal panels. A light-emitting device which emits white lightis provided as a white light source device at the back of the liquidcrystal panel. The liquid crystal panel is used as a light modulationelement of transmission-type, and forms an image by controlling thetransmittance of light irradiated from the light-emitting device.Conventionally, as these light-emitting devices, a cold cathodefluorescent lamp (CCFL) or a super-high pressure mercury (UHP: ultrahigh performance) lamp has been used. However, with intent to conserveenergy and reduce the use of mercury in consideration of environment, assuch a light source, recent years have seen development of alight-emitting device in which a semiconductor light-emitting element,such as a light emitting diode (LED), in combination with a phosphoroptical element that obtains fluorescent light by converting withphosphor the light from the semiconductor light-emitting element.

There are light-emitting device of (i) a phosphor integral-type in whicha semiconductor light-emitting element and a phosphor optical elementare disposed on the same package and (ii) a phosphor separation-type inwhich a semiconductor light-emitting element and a phosphor opticalelement are disposed at separate locations within a display device.

In both types of the light-emitting device, in the phosphor opticalelement, fluorescent light from phosphors is emitted omnidirectionally.Thus, there are needs of optical systems which efficiently collectfluorescent light or improving directivity of fluorescent light.

Conventionally, there is a technique for improving efficiency inutilizing fluorescent light. For example, patent literature (PTL) 1discloses a technique in which a dichroic mirror is disposed between anLED element and resin which includes phosphors to reflect, among theomnidirectionally emitted fluorescent light, the light that travelstoward an LED element. The following describes a conventionallight-emitting device 1000 using FIG. 14.

As shown in FIG. 14, the conventional light-emitting device 1000includes: a recessed case 1004 including an opening 1042; an LED element1002 which is a light source for exciting phosphors and is mounted on anelement mounting surface 1040 that is a base of the recess of the case1004; and a dichroic mirror 1003 provided above the LED element 1002.Furthermore, above the LED element 1002, a phosphor-containing siliconeresin 1008 that is a silicone resin including rare-earth activatedphosphors, such as YAG:Ce or the like having a particle diameter of 10to 20 μm, is formed via a silicone resin 1007. The side surface of therecess of the case 1004 (i) is a tilted face 1041 that is formedobliquely with respect to a light-emitting direction of the LED element1002, and (ii) has a function of reflecting, toward the front directionof the light-emitting device 1000, the fluorescent light emitted fromthe phosphor-containing silicone resin 1008 together with the lightemitted from the LED element 1002.

In the light-emitting device 1000 having the above-describedconfiguration, the light emitted from the LED element 1002 passesthrough the silicone resin 1007 and enters the phosphor-containingsilicone resin 1008. A portion of the light which entered thephosphor-containing silicone resin 1008 is reflected, and anotherportion of the light is absorbed by the phosphors to be emitted asfluorescent light. The fluorescent light from the phosphor-containingsilicone resin 1008 is omnidirectionally emitted, and due to multiplereflections by the tilted face 1041, a dichroic mirror 1003, and thelike, and is emitted to outside of the light-emitting device 1000through the entire surface of the opening 1042.

Furthermore, PTL 2 discloses a light-emitting device that uses, as alight source of a projector, fluorescent light obtained by causing lightfrom an excitation light source to incident on a phosphor light emittingelement in which a dichroic mirror and a phosphor are used incombination.

CITATION LIST Patent Literature

-   [PTL 1]-   Japanese Unexamined Patent Application Publication No. 2006-186022-   [PTL 2]-   Japanese Unexamined Patent Application Publication No. 2010-198805

SUMMARY Technical Problem

However it is difficult for a conventional phosphor optical element toefficiently emit the obtained fluorescent light in a predetermineddirection with a desired light-emitting area, which is problematic. Morespecifically, it is possible to emit the fluorescent light in apredetermined direction, by using a member containing a phosphor (aphosphor-containing member) and the dichroic mirror in combination.However, the fluorescent light can freely propagate in the planardirection of a layer of the phosphor-containing member. This causes thefluorescent light to be emitted from the entire surface of thephosphor-containing member and increases the light-emitting area of thefluorescent light, which is problematic. In this case, when thefluorescent light emitted from the phosphor optical element is convertedinto parallel light using a lens or the like, an oblique light componentincreases, which results in a loss for an optical system at a subsequentstage. Consequently, the efficiency of the optical system decreases. Inview of such a problem, for example, it is possible to reduce an area ofthe phosphor-containing member. However, in this case, thephosphor-containing member and the light-emitting element need to bealigned with higher accuracy, which leads to an increase in the cost ofthe phosphor optical element.

The present disclosure is conceived to solve the above-describedproblem, and one non-limiting and exemplary embodiment provides aphosphor optical element and a light-emitting device which can easilyreduce the light-emitting area of fluorescent light without reducing thearea of a phosphor-containing member.

Solution to Problem

In view of the above-described problem, in one general aspect, thetechniques disclosed here feature a phosphor optical element including:a base member; a phosphor-containing member that includes a transparentmember containing a phosphor particle; and a cover member, wherein thebase member, the phosphor-containing member, and the cover member aresequentially formed on a transparent base that is transparent to awavelength of incident light emitted from an excitation light source,the phosphor particle has a diameter no greater than the wavelength ofthe incident light, and in an arbitrary cross section of thephosphor-containing member in a direction perpendicular to a mainsurface of the transparent base, the phosphor-containing member has, inat least one of (i) a direction perpendicular to and (ii) a directionhorizontal to the main surface of the transparent base, a thickness nogreater than the wavelength of the incident light.

With this configuration, it is possible to reduce a chance for a portionof the fluorescent light generated by the phosphor particle to propagatein a direction parallel to the main surface of the transparent base.Thus, the light-emitting area of the fluorescent light can beapproximately the same as an area on which incident light emitted fromthe excitation light source incidents.

Furthermore, in the aspect of the phosphor optical element according tothe present disclosure, it may be that at least one of the base memberand the cover member includes a multilayer film whose layers are stackedin a direction perpendicular to the transparent base. In this case, forexample, the multilayer film is a dielectric multilayer film.

With this configuration, it is possible to reduce a chance for a portionof the fluorescent light generated by the phosphor particle to propagatein a direction parallel to the main surface of the transparent base, andguide the florescent light in a predetermined emission direction.

Furthermore, in the aspect of the phosphor optical element according tothe present disclosure, for example, the base member transmits theincident light and reflects fluorescent light emitted from thephosphor-containing member.

With this configuration, it is possible to reduce a chance for a portionof the fluorescent light generated by the phosphor particle to propagatein a direction parallel to the main surface of the transparent base, andguide the florescent light in a predetermined emission direction.

Furthermore, in the aspect of the phosphor optical element according tothe present disclosure, it may be that the phosphor-containing memberhas, in a two dimensional planar direction that is a direction parallelto the main surface of the transparent base, a refractive indexdistribution according to a two-dimensional periodic structure. In thiscase, the two-dimensional periodic structure may include a photoniccrystal.

With this configuration, it is possible to reduce a chance for a portionof the fluorescent light generated by the phosphor particle to propagatein a direction parallel to the main surface of the transparent base, andguide the florescent light in a predetermined emission direction.

Furthermore, in the aspect of the phosphor optical element according tothe present disclosure, it may be that the phosphor-containing memberincludes two types of transparent materials having different refractiveindices, and the phosphor particle is included in at least one of thetwo types of transparent materials having different refractive indices.

With this configuration, it is possible to reduce a chance for a portionof the fluorescent light generated by the phosphor particle to propagatein a direction parallel to the main surface of the transparent base, andguide the florescent light in a predetermined emission direction.

Furthermore, in the aspect of the phosphor optical element according tothe present disclosure, at least one of the two types of transparentmaterials having different refractive indices may include ZnO.

With this configuration, a phosphor-containing optical element can beeasily configured which can reduce a chance for a portion of thefluorescent light generated by the phosphor particle to propagate in adirection parallel to the main surface of the transparent base, andguide the florescent light in a predetermined emission direction.

Furthermore, in the aspect of the phosphor optical element according tothe present disclosure, a topmost layer of the base member may be a ZnOfilm.

With this configuration, a phosphor-containing optical element can beeasily configured which can reduce a chance for a portion of thefluorescent light generated by the phosphor particle to propagate in adirection parallel to the main surface of the transparent base, andguide the florescent light in a predetermined emission direction.

Furthermore, in one general aspect, the techniques disclosed herefeature a light-emitting device including: the phosphor optical elementdescribed above; and a light-emitting element that is an excitationlight source, wherein the light-emitting element has an optical axisperpendicular to a surface of the transparent base of the phosphoroptical element.

With this configuration, the wavelength of the light emitted from alight-emitting element can be easily converted with a simpleconfiguration, and the propagation direction of light can be controlled.

Additional benefits and advantages of the disclosed embodiments will beapparent from the Specification and Drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the Description and Drawings, which need not all be providedin order to obtain one or more of such benefits and/or advantages.

Advantageous Effects

The present disclosure makes it possible to easily reduce alight-emitting area of fluorescent light without decreasing an area of aphosphor-containing member. With this, the traveling direction of lightcan be freely controlled with an optical system or the like which isprovided in a subsequent stage.

BRIEF DESCRIPTION OF DRAWINGS

These and other advantages and features will become apparent from thefollowing description thereof taken in conjunction with the accompanyingDrawings, by way of non-limiting examples of embodiments disclosedherein.

FIG. 1 is a cross-sectional view showing a configuration of a phosphoroptical element according to Embodiment 1.

FIG. 2 is a diagram for describing operations of the phosphor opticalelement according to Embodiment 1.

FIG. 3A is a diagram showing calculation parameters for describingfunctions of the phosphor optical element according to Embodiment 1.

FIG. 3B is a diagram showing transmittance of a base member and a covermember in the phosphor optical element according to Embodiment 1, whichis obtained based on the calculation parameters in FIG. 3A.

FIG. 3C is a diagram showing light intensity of excitation light andfluorescent light in the phosphor optical element according toEmbodiment 1.

FIG. 4 is a diagram for describing a configuration and operations of alight-emitting device using the phosphor optical element according toEmbodiment 1.

FIG. 5 is a cross-sectional view showing a configuration of a phosphoroptical element according to a modification of Embodiment 1.

FIG. 6A is a cross-sectional view showing a configuration of a phosphoroptical element according to Embodiment 2.

FIG. 6B is a cross-sectional view showing a configuration of thephosphor optical element according to Embodiment 2, taken along a lineA-A of FIG. 6A.

FIG. 7 is a diagram for describing operations of the phosphor opticalelement according to Embodiment 2.

FIG. 8A is a diagram for describing calculation parameters fordescribing functions of the phosphor optical element according toEmbodiment 2.

FIG. 8B is a diagram showing transmittance of a phosphor-containinglayer in the phosphor optical element according to Embodiment 2, whichis calculated based on the calculation parameters in FIG. 8A.

FIG. 8C is a diagram showing light intensity of excitation light andfluorescent light in the phosphor optical element according toEmbodiment 2.

FIG. 9 shows cross-sectional views for describing processes in a methodof manufacturing the phosphor optical element according to Embodiment 2.

FIG. 10 is a cross-sectional view showing a configuration of a phosphoroptical element according to Modification 1 of Embodiment 2.

FIG. 11 is a cross-sectional view showing a configuration of a phosphoroptical element according to Modification 2 of Embodiment 2.

FIG. 12A is a cross-sectional view showing a configuration of a phosphoroptical element according to Modification 3 of Embodiment 2

FIG. 12B is a cross-sectional view showing a configuration of thephosphor optical element according to Modification 3 of Embodiment 2,taken along a line A-A of FIG. 12A.

FIG. 13 is a diagram for describing a configuration and operations of alight-emitting device using the phosphor optical element according toEmbodiment 2.

FIG. 14 is a cross-sectional view showing a configuration of alight-emitting device according to a conventional example.

DESCRIPTION OF EMBODIMENTS

Hereinafter, certain exemplary embodiments are described in greaterdetail with reference to the accompanying Drawings. Each of theexemplary embodiments described below shows a general or specificexample. The numerical values, shapes, materials, structural elements,the arrangement and connection of the structural elements, steps, theprocessing order of the steps etc. shown in the following exemplaryembodiments are mere examples, and therefore do not limit the presentdisclosure. The present disclosure is defined by Claims. Therefore,among the structural elements in the following exemplary embodiments,structural elements not recited in any one of the independent claimsdefining the most generic part of the inventive concept are notnecessarily required to solve the problem of the present disclosure, butare described as structural elements of a more preferable form.Furthermore, elements having substantially the same configurations,operations, and effects are denoted with the same reference signs in thedrawings.

Embodiment 1

The following describes a phosphor optical element and a light-emittingdevice according to Embodiment 1 of the present disclosure. First, thephosphor optical element according to Embodiment 1 of the presentdisclosure is described using FIG. 1. FIG. 1 is a cross-sectional viewshowing a configuration of the phosphor optical element according tothis embodiment.

As shown in FIG. 1, a phosphor optical element 1 according to thisembodiment is a light-emitting element which emits fluorescent lightwith incident light from an excitation light source, and includes: atransparent base 10; and a stacked structure including, a base member20, a phosphor-containing member 30, and a cover member 40 which areformed sequentially on the transparent base 10.

The transparent base 10 includes a material transparent to a wavelengthof an incident light from the excitation light source. For example, thetransparent base 10 may be a transparent board made of glass, atransparent resin film, or the like.

The base member 20 is a dielectric multilayer film that includes: afirst base layer 21 (a first layer) having, for example, a structure inwhich a second refractive index layer 21 b including TiO₂ is betweenfirst refractive index layers 21 a including ZnO; and a second baselayer 22 (a second layer) including, for example, SiO₂. The layers arestacked in a direction perpendicular to a main surface (the surface) ofthe transparent base 10. The base member 20 includes the first baselayer 21 and the second base layer 22 that are alternately stacked, andis a multilayer film in which, for example, five or more layers made upof the first base layers 21 and the second base layers 22 are stacked.The base member 20 in this embodiment includes seven layers, that is,four layers of the first base layer 21 and three layers of the secondbase layer 22. Note that, each of the bottommost layer and the topmostlayer of the base member 20 is the first base layer 21 that is a ZnOfilm.

Furthermore, the base member 20 is transparent to a wavelength of anincident light (excitation light) from the excitation light source, andacts as a mirror to a wavelength of the fluorescent light emitted fromthe phosphor-containing member 30. More specifically, the base member 20functions as a first dichroic mirror which transmits the excitationlight and reflects the fluorescent light from the phosphor-containingmember 30.

The phosphor-containing member 30 is a phosphor-containing layer stackedon the base member 20, and includes: a transparent member 31 including atransparent material; and phosphor particles 32 which are included inthe transparent member 31 and emit fluorescent light with incident light(excitation light) from the excitation light source. As each of thephosphor particles 32, for example, a semiconductor particle having aparticle diameter of 100 nm or less, such as an InP/ZnS core shellquantum dot phosphor, can be used. With the quantum dot phosphor, evenin the case of particles of an identical material, the fluorescent lightspectrum of a desired wavelength range in a visible light range can beobtained by controlling the diameter of a particle because of a quantumsize effect. Furthermore, as the transparent member 31, a transparentresin material, such as a silicone resin having a refractive index of1.4 can be used, for example.

The cover member 40 is formed on the phosphor-containing member 30, andis a dielectric multilayer film that includes: a first cover layer 41 (athird layer) in which, for example, a fourth refractive index layer 41 bincluding TiO₂ is between third refractive index layers 41 a includingZnO; and a second cover layer 42 (a fourth layer) including, forexample, SiO₂. The layers are alternately stacked in a directionperpendicular to the main surface of the transparent base 10. The covermember 40 includes the first cover layer 41 and the second cover layer42 that are alternately stacked, and is a multilayer film in which, forexample, five or more layers made up of the first cover layers 41 andthe second cover layers are stacked. The cover member 40 in thisembodiment includes eight layers, that is, four layers of the firstcover layer 41 and four layers of the second cover layer 42.

Furthermore, in contrast to the base member 20, the cover member 40 actsas a mirror to a wavelength of the incident light (excitation light)from the excitation light source, and is transparent to a wavelength ofthe fluorescent light emitted from the phosphor-containing member 30.More specifically, the cover member 40 functions as a second dichroicmirror which reflects the excitation light and transmits the fluorescentlight from the phosphor-containing member 30.

In the phosphor optical element 1 having the above-describedconfiguration, the diameter of the phosphor particle 32 in thephosphor-containing member 30 is configured to be no greater than awavelength of the incident light from the excitation light source.Furthermore, in the arbitrary cross section of the phosphor-containingmember 30 in the direction perpendicular to the main surface of thetransparent base 10, the thickness of the phosphor-containing member 30in the direction perpendicular to the main surface of the transparentbase 10 (stacking direction), that is, the film thickness of thephosphor-containing member 30 is also configured to be no greater than awavelength of the incident light from the excitation light source.

With this configuration, for example, the phosphor particles 32 in thephosphor-containing member 30 perform long wavelength conversion on theexcitation light (incident light) having a wavelength of 405 nm andemit, for example, fluorescent light having a peak wavelength of 540 nm,and a full width at half maximum of 50 nm of the spectrum. In this case,the thickness of the phosphor-containing member 30 in theabove-described cross-section is set to be no greater than thewavelength of the excitation light, that is, no greater than 405 nm.More specifically, the thickness of the phosphor-containing member 30 inthe above-described cross-section is set to, for example, approximatelyno greater than 390 nm that is the resulting wavelength by dividing thepeak wavelength (540 nm) of fluorescent light by the refractive index(1.4) of the transparent member 31.

Next, operations of the phosphor optical element 1 having theabove-described configuration are described using FIG. 2. FIG. 2 is adiagram for describing operations of a phosphor optical elementaccording to this embodiment.

As shown in FIG. 2, incident light 63 which is from the excitation lightsource and enters from the transparent base 10 side passes through thetransparent base 10 and the base member 20, and enters thephosphor-containing member 30. A portion of the incident light 63 whichentered the phosphor-containing member 30 is converted into thefluorescent light 65 and emitted by the phosphor particles 32. On theother hand, another portion of the incident light 63 not absorbed by thephosphor particles 32 passes through the phosphor-containing member 30.The incident light 63 which passed through the phosphor-containingmember 30 is reflected by the cover member 40, and enters thephosphor-containing member 30 again. The light which entered thephosphor-containing member 30 again is converted into the fluorescentlight 65 by the phosphor particles 32. In this manner, the light whichpassed through the phosphor-containing member 30 is reflected by thecover member 40, and enters the phosphor-containing member 30 again.Thus, the incident light 63 can be efficiently converted into thefluorescent light 65.

The fluorescent light 65 generated in the phosphor-containing member 30is omnidirectionally emitted. Among this, the fluorescent light 65 whichentered the cover member 40 passes through the cover member 40, and isemitted in a predetermined emission direction. On the other hand, thefluorescent light 65 which travels toward the base member 20 isreflected by the base member 20, passes through the phosphor-containingmember 30 and the cover member 40, and is emitted in a predeterminedemission direction.

In this case, in the phosphor optical element 1 according to thisembodiment, as described above, the phosphor-containing member 30 isconfigured to have a film thickness no greater than the wavelength ofthe incident light 63 (excitation light). Thus, the film thickness ofthe phosphor-containing member 30 is thin enough with respect to thefluorescent light 65. With this, the fluorescent light 65 scarcelypropagates in a planar direction of the phosphor-containing member 30that is a two dimensional direction parallel to the main surface of thetransparent base 10 (a direction perpendicular to the stackingdirection). Thus, the light-emitting area of the fluorescent light 65can be about the same size as the area on which the incident light 63(excitation light) incidents, which makes it possible to easily reducethe light-emitting area of the fluorescent light 65 without reducing thearea of the phosphor-containing member 30. As a result, the travelingdirection of light can be freely controlled using an optical system orthe like disposed in a stage subsequent to the phosphor optical element1.

Next, operations of the phosphor optical element 1 according to thisembodiment in FIG. 2 are described based on the calculation results ofFIG. 3A, FIG. 3B, and FIG. 3C. FIG. 3A is a diagram showing calculationparameters for describing functions of a phosphor optical elementaccording to this embodiment. FIG. 3B is a diagram showing transmittanceof a base member and a cover member in the phosphor optical elementaccording to this embodiment, which is obtained using the calculationparameters in FIG. 3A. FIG. 3C is a diagram showing light intensity ofexcitation light and fluorescent light in the phosphor optical elementaccording to this embodiment.

Here, as shown in FIG. 3C, the wavelength of the excitation light (theincident light 63) is 405 nm, and the excitation light in thisembodiment is laser light. The fluorescent light 65 has a peakwavelength of 540 nm, and is light from the phosphor particles 32 whichinclude quantum dot phosphors.

As shown in FIG. 3B, according to the transmittance of the base member20 and the cover member 40 obtained using the calculation parameters inFIG. 3A, the base member 20 transmits the incident light 63 having awavelength of 405 nm, while reflecting most of the fluorescent light 65having a central wavelength of 540 nm. Furthermore, it is indicated thatthe cover member 40 reflects the incident light 63 having a wavelengthof 405 nm, while transmitting the fluorescent light 65 having a centralwavelength of 540 nm.

In this manner, in this embodiment, the phosphor-containing member 30 isbetween the dichroic mirrors of the base member 20 and the cover member40. Thus, as described in FIG. 2, the incident light 63 passes throughthe base member 20 and is reflected by the cover member 40. This makesit possible to efficiently generate the fluorescent light 65 in thephosphor-containing member 30. Furthermore, the fluorescent light 65generated in the phosphor-containing member 30 passes through the covermember 40, and is reflected by the base member 20. Thus, the obtainedfluorescent light 65 can be efficiently emitted to the outside of thephosphor optical element 1. Furthermore, in this embodiment, thephosphor-containing member 30 is configured to have a thickness nogreater than a wavelength of the incident light 63 (excitation light).Thus, the fluorescent light scarcely propagates in a planar direction ofthe phosphor-containing member 30. Thus, the light-emitting area of thefluorescent light 65 can be reduced without reducing the area of thephosphor-containing member 30.

Next, a configuration and operations of a light-emitting device 99 usinga phosphor optical element 1 shown in FIG. 1 is described using FIG. 4.FIG. 4 is a diagram for describing a configuration and operations of alight-emitting device using the phosphor optical element according tothis embodiment.

As shown in FIG. 4, the light-emitting device 99 according to thisembodiment includes: the phosphor optical element 1; and alight-emitting element 50 that is an excitation light source including aplurality of semiconductor lasers (semiconductor light-emittingelements). The optical axis of the light-emitting element 50 isperpendicular to the surface of the transparent base 10 in the phosphoroptical element 1. Furthermore, the light-emitting device 99 includes: aplurality of collimating lenses 52 arranged at light emitting positionsof a plurality of the light-emitting elements 50; a plurality ofreflecting mirrors 54 arranged in front (light traveling direction) ofthe collimating lenses 52, corresponding to the collimating lenses 52;and a collecting lens 56 disposed in the light path of reflected lightfrom the reflecting mirrors 54 to collect all the light reflected by thereflecting mirrors 54. The phosphor optical element 1 is disposed withthe phosphor-containing member 30 of the phosphor optical element 1aligned at a light-converging position of the collecting lens 56. Inother words, the phosphor-containing member 30 of the phosphor opticalelement 1 is disposed at the focal point of the collecting lens 56. Notethat, on a light emission side of the phosphor optical element 1, acollimating lens 58 is disposed at a position facing the phosphoroptical element 1.

Subsequently, operations of the light-emitting device 99 are described.First, emitted light 60 (excitation light) emitted from thelight-emitting elements 50 becomes parallel light 61 with thecorresponding collimating lenses 52, and then becomes parallel light 62having light propagation area which has been shaped with the reflectingmirrors 54. The parallel light 62 becomes converged light by thecollecting lens 56, and enters the phosphor optical element 1 as theincident light 63 and converges at the phosphor-containing member 30. Inthe phosphor-containing member 30, the incident light 63 is convertedinto the fluorescent light 65 with the semiconductor particles, andemitted from the phosphor optical element 1. The fluorescent light 65emitted from the phosphor optical element 1 is converted into parallellight 67 by the collimating lens 58.

With the light-emitting device 99 according to this embodiment, thelight emitted from the phosphor optical element 1 can be easilyconverted into parallel light by the collimating lens 58, because thelight-emitting area of the fluorescent light 65 can be reduced with thephosphor optical element 1. In this manner, with the light-emittingdevice 99, the light-emitting area of the fluorescent light 65 generatedby the phosphor optical element 1 can be reduced. Thus, the travelingdirection of light can be freely controlled with the optical system orthe like that is disposed in the stage subsequent to the phosphoroptical element 1.

Next, a phosphor optical element 1A according to a modification ofEmbodiment 1 of the present disclosure is described using FIG. 5. FIG. 5is a cross-sectional view showing a configuration of a phosphor opticalelement according to the modification of this embodiment. Note that, theconfiguration of the phosphor optical element 1A according to thismodification is substantially the same as the configuration of thephosphor optical element 1 according to Embodiment 1. Thus, thismodification mainly describes portions different from Embodiment 1. Notethat, in FIG. 5, the same structural elements as those in FIG. 1 aredenoted with the same reference signs.

Compared to the phosphor optical element 1 according to Embodiment 1shown in FIG. 1, the phosphor optical element 1A according to thismodification is different in a configuration of a phosphor-containingmember as shown in FIG. 5. A phosphor-containing member 30A according tothis modification includes a plurality of layers each including atransparent material.

More specifically, in the phosphor optical element 1A according to thismodification, the phosphor-containing member 30A includes: twophosphor-containing members, namely, a first phosphor-containing member30 a and a second phosphor-containing member 30 b; and a transparentmember 35 formed between the first phosphor-containing member 30 a andthe second phosphor-containing member 30 b.

Each of the first phosphor-containing member 30 a and the secondphosphor-containing member 30 b includes, as with thephosphor-containing member 30 in FIG. 1, the transparent member 31 andthe phosphor particles 32 included in the transparent member 31. Here,for example, the transparent member 31, which is included in the firstphosphor-containing member 30 a and the second phosphor-containingmember 30 b, and the transparent member 35 are formed of transparentmaterials having different refractive indices. Furthermore, thetransparent member 35 is formed only of the transparent material, thatis, the phosphor particles are not included.

In this modification as well, each of the phosphor-containing members,namely, the first phosphor-containing member 30 a and the secondphosphor-containing member 30 b is set to have a thickness no greaterthan wavelengths of the fluorescent light and the incident light, aswith Embodiment 1. With this configuration, even in the case where thethickness of each of the phosphor-containing members is increased and aneffective amount of the phosphor particles is increased, propagation offluorescent light in the horizontal direction can be reduced because thethickness of each of the phosphor-containing members is no greater thanwavelengths of the fluorescent light and the incident light. Thus, thefluorescent light can have a small light-emitting area.

Note that, although both of the first phosphor-containing member 30 aand the second phosphor-containing member 30 b include the phosphorparticles 32 in this modification, it may be that only one of the firstphosphor-containing member 30 a and the second phosphor-containingmember 30 b include the phosphor particles 32.

The phosphor optical element and the light-emitting device according toEmbodiment 1 have been thus far described. However, the presentdisclosure is not limited to the above-described embodiments ormodifications.

For example, in the light-emitting device 99 according to thisembodiment shown in FIG. 4, a semiconductor laser is used as thelight-emitting element 50. However, a super luminescent diode may beused as a light-emitting element of an end-face emission type in whichan optical waveguide is formed. Furthermore, although a semiconductorlaser, which is the excitation light source, having an emissionwavelength of 405 nm is described, a semiconductor laser which emits thelight having a wavelength, for example, from 420 nm to 490 nm may beused.

Furthermore, the phosphor particle 32 of the phosphor-containing member30 in the phosphor optical element 1 according to this embodiment is theInP/ZnS core shell quantum dot phosphor, but is not limited thereto. Asthe material of the quantum dot phosphor, for example, at least oneselected from InN, InP, InAs, InSb, GaN, GaP, GaAs, GaSb, AlN, AlP,AlAs, AlSb, and BN that are Group II-V compound semiconductors, at leastone selected from HgS, HgSe, HgTe, CdS, CdSe, CdTe, ZnS, ZnSe, and ZnTethat are Group II-VI compound semiconductors, or at least one selectedfrom the group consisting of mixed crystal of the above can be used.

Furthermore, although the phosphor particle 32 in this embodiment is anondoped quantum dot phosphor, a doped quantum dot phosphor may be used.As the material included in the doped quantum dot phosphor, for example,at least one from ZnS:Mn²⁺, CdS:Mn²⁺, and YVO₄:Eu³⁺ can be used.Furthermore, in a broader sense, it is sufficient that the phosphorparticle 32 be a phosphor particle which (i) has a size no greater thanthe wavelength of the fluorescent light and, (ii) is a phosphor particlehaving a reduced non-light emission recombination loss caused by surfaceflaws. For example, YAG:Ce nanoparticles may be used.

Furthermore, a resin material of the transparent member 31 in thisembodiment is a silicone resin, but is not limited thereto. As a resinmaterial of the transparent member 31, other than the silicone resin, atransparent resin material such as an acrylic resin, an epoxy resin, orthe like can be used. Furthermore, the transparent member 31 need notinclude a resin material and, for example, may include an inorganictransparent material, such as low melting point glass. In this case, thephosphor-containing member 30 can be configured by mixing into theinorganic transparent material the phosphor particle 32 having aparticle diameter no greater than the wavelength of fluorescent light.

Furthermore, the first base layer 21, the second base layer 22, thefirst cover layer 41, and the second cover layer 42 in this embodimentare a multilayer film including a combination of ZnO, TiO₂, and SiO₂,but are not limited thereto. For example, the base member 20 and thecover member 40 may be a dielectric multilayer film including a lowrefractive index material and a high refractive index material. As thematerial having a low refractive index, for example, one of Bi₂O₃,Ta₂O₅, La₂O₃, Al₂O₃, SiO_(x) (x≦1), LaF₃, a complex oxide of La₂O₃ andAl₂O₃, and a complex oxide of Pr₂O₃ and Al₂O₃, or an complex oxide of atleast two materials selected from the above, or a dielectric materialsuch as a fluoride or the like, such as CaF₂, MgF₂, or LiF can be used.Furthermore, as a material having a high refractive index, for example,(i) one of TiO₂, Nb₂O₅, and Ta₂O₅ or (ii) a complex oxide or the likeincluding as a main component one of TiO₂, Nb₂O₅, and Ta₂O₅ can be used.

Embodiment 2

Next, a phosphor optical element according to Embodiment 2 of thepresent disclosure is described using FIG. 6A and FIG. 6B. FIG. 6A is across-sectional view showing a configuration of a phosphor opticalelement according to this embodiment. FIG. 6B is a cross-sectional viewshowing a configuration of the phosphor optical element according tothis embodiment, taken along a line A-A of FIG. 6A. Note that, in FIG.6A, the same structural elements as those in FIG. 1 are denoted with thesame reference signs, and their descriptions are omitted or simplified.

As shown in FIG. 6A and FIG. 6B, the phosphor optical element 100according to this embodiment is a light-emitting element that emitsfluorescent light with incident light from an excitation light source,and includes: a transparent base 10 which includes, for example, glass,a transparent resin film, or the like; and a stacked structure whichincludes a base member 120, a phosphor-containing layer 130 and a covermember 240 which are sequentially formed on the transparent base 10.

The base member 120 is a dielectric multilayer film which is formed of afirst base layer 121 in which, for example, a second refractive indexlayer 121 b including TiO₂ is between first refractive index layers 121a including ZnO; and a second base layer 122 that includes, for example,SiO₂. The layers are stacked in a direction perpendicular to a mainsurface (the surface) of the transparent base 10. The base member 120includes the first base layer 121 and the second base layer 122 that arealternately stacked, and is a multilayer film in which, for example,five or more layers made up of the first base layers 121 and the secondbase layers 122 are stacked. The base member 120 in this embodimentincludes seven layers, that is, four layers of the first base layer 121and three layers of the second base layer 122. Note that, each of thebottommost layer and the topmost layer of the base member 120 is thefirst base layer 121 that is the ZnO film.

Furthermore, the base member 120 is transparent to a wavelength ofincident light (excitation light) from the excitation light source, andacts as a mirror to a wavelength of the fluorescent light emitted fromthe phosphor-containing layer 130. More specifically, the base member120 functions as a first dichroic mirror which transmits the excitationlight, and reflects the fluorescent light from the phosphor-containinglayer 130.

The phosphor-containing layer 130 is formed on the base member 120, andincludes a phosphor-containing member 133 and a transparent member 135.The phosphor-containing member 133 includes: a transparent member 131which includes a transparent material; and phosphor particles 132 whichare included in the transparent member 131 and emit fluorescent lightwith incident light (excitation light) from the excitation light source.Each of the phosphor particles 132 may be, for example, a semiconductorparticle having a particle diameter no greater than 100 nm, such as anInP quantum dot phosphor. The transparent member 131 is a firsttransparent member, and may include, for example, a transparentmaterial, such as a silicone resin having a refractive index of 1.4.

The transparent member 135 is a second transparent member including aplurality of cylindrical rods each of which includes a transparentmaterial and stand on the base member 120 to have a positionalrelationship that forms a triangular lattice as shown in FIG. 6B. Inthis embodiment, the transparent member 135 includes only a transparentmaterial. Furthermore, as shown in the figure, the phosphor-containingmember 133 in the phosphor-containing layer 130 is formed to fill thespace between the columnar transparent members 135 which are standing.As a transparent material of the transparent member 135, for example, amaterial having a different refractive index than a transparent materialof the transparent member 131 of the phosphor-containing member 133 maybe used. For example, ZnO having a refractive index of 2.0 may be used.

In this manner, the phosphor-containing layer 130 in this embodimentincludes the phosphor-containing member 133 and the transparent member135 which are alternately arranged in a two dimensional planar directionthat is a direction parallel to the main surface of the transparent base10, and is configured to have a refractive index distribution accordingto a two-dimensional periodic structure. Such a two-dimensional periodicstructure can also be configured with, for example, a photonic crystalthat is a nanostructure having a refractive index that changesperiodically.

The cover member 240 is a transparent board including a transparentmaterial such as glass or the like, and is formed on thephosphor-containing layer 130. The cover member 240 according to thisembodiment is a single glass board.

In the phosphor optical element 100 having the above-describedconfiguration, the phosphor particle 132 in the phosphor-containingmember 133 is configured to have a particle diameter no greater than awavelength of the incident light from the excitation light source.Furthermore, in the arbitrary cross section of the phosphor-containinglayer 130 in the direction perpendicular to the main surface of thetransparent base 10, the thickness of the phosphor-containing member 133in a direction horizontal to the main surface of the transparent base10, that is, a thickness of the phosphor-containing layer 130 in thehorizontal direction excluding the thickness of the transparent member135 is also configured to be no greater than the wavelength of theincident light from the excitation light source.

With this configuration, for example, the phosphor particles 132 of thephosphor-containing member 133 perform long wavelength conversion on theexcitation light (incident light) having a wavelength of 450 nm, andemit, for example, fluorescent light having a peak wavelength of 540 nm.In this case, the thickness of the phosphor-containing member 133 in theabove-described cross-section that is a pitch of the transparent members135 formed to be a triangular lattice is no greater than 450 nm that isthe wavelength of the excitation light. More specifically, the thicknessof the phosphor-containing member 133 in the above-describedcross-section is set to, for example, no greater than 380 nm that is theresulting wavelength by dividing the peak wavelength (540 nm) offluorescent light by the refractive index (1.4) of the transparentmember 131.

Next, operations of the phosphor optical element 100 according to thisembodiment having the above-described configuration are described usingFIG. 7. FIG. 7 is a diagram for describing operations of a phosphoroptical element according to this embodiment.

As shown in FIG. 7, incident light 163 which is from the excitationlight source and enters from the transparent base 10 side passes throughthe transparent base 10 and the base member 120, and enters thephosphor-containing layer 130. A portion of the incident light 163 whichentered the phosphor-containing layer 130 is converted into fluorescentlight 165 by the phosphor particles 132, and another portion of theincident light 163 not absorbed by the phosphor particles 132 passesthrough the phosphor-containing layer 130. A portion of the incidentlight 163 which passed through the phosphor-containing layer 130 isreflected by the cover member 240, and then enters thephosphor-containing layer 130 again. A portion of the light whichentered the phosphor-containing layer 130 again is converted intofluorescent light 165 by the phosphor particles 132.

The fluorescent light 165 obtained as a result of the conversion in thephosphor-containing layer 130 or the incident light 163 reflected by thephosphor particles 132 is omnidirectionally emitted. Among this, thefluorescent light 165 which entered the cover member 240 passes throughthe cover member 240, and is emitted in a predetermined emissiondirection. On the other hand, the fluorescent light 165 which travelstoward the base member 120 is reflected by the base member 120, passesthrough again the phosphor-containing layer 130 and the cover member240, and is emitted in a predetermined emission direction.

In this case, as described above, in the phosphor optical element 100according to this embodiment, to allow the phosphor-containing member133 to have a thickness no greater than a wavelength of the incidentlight 163 (excitation light), the phosphor-containing layer 130 has aperiodic structure with which the fluorescent light 165 is less likelyto propagate in a planar direction. Thus, the fluorescent light 165scarcely propagates in a planar direction of the phosphor-containinglayer 130 that is a two dimensional direction parallel to the mainsurface of the transparent base 10. Thus, the light-emitting area of thefluorescent light 165 can be about the same size as the area on whichthe incident light 163 (excitation light) incidents. This makes itpossible to easily reduce the light-emitting area of the fluorescentlight 165 without reducing the area of the phosphor-containing layer130. As a result, the traveling direction of light can be freelycontrolled with an optical system or the like which is disposed in astage subsequent to the phosphor optical element 100.

Next, operations of the phosphor optical element 100 according to thisembodiment in FIG. 7 is described based on the calculation results ofFIG. 8A, FIG. 8B, and FIG. 8C. FIG. 8A is a diagram for describingcalculation parameters for describing functions of the phosphor opticalelement according to this embodiment. Specifically, the diagram on theleft in FIG. 8A shows the phosphor-containing layer 130 in thecross-sectional direction in a similar manner as FIG. 6B, and definesthat the pitch of the transparent member 135 is P, and the diameter isD. Furthermore, it is assumed that the incident light 163 is convertedinto the fluorescent light 165 at an arbitrary point, and thefluorescent light 165 enters at angle θ the transparent member 135,which is disposed to form a triangular lattice, and propagates adistance L. At this time, the transmittance of the phosphor-containinglayer 130 in the phosphor optical element 100 according to thisembodiment is shown in FIG. 8B based on the calculation parameters inthe diagram on the right in FIG. 8A. Note that, FIG. 8B shows thetransmittance in the cases where the angles θ are 0 degree and 15degrees. Furthermore, FIG. 8C is a diagram showing spectrums of theincident light 163 and the fluorescent light 165 for describing effectsof characteristics of the transmittance of the phosphor-containing layer130.

Here, the excitation light (the incident light 163) has a wavelength of450 nm, and the excitation light in this embodiment is laser light. Itis assumed that the fluorescent light 165 has a peak wavelength of 540nm, and is the light from the phosphor particles 132 including quantumdot phosphors.

As shown in FIG. 8B, according to the transmittance of thephosphor-containing layer 130 obtained using the calculation parametersin FIG. 8A, the phosphor-containing layer 130 scarcely propagates, inthe planar direction, light having a wavelength from 520 nm to 580 nm ina range within a propagation distance of 3 μm. Such light is notabsorbed by the phosphor-containing layer 130, cannot propagate towardthe base member 120, and thus travels toward the above of the phosphoroptical element 100, that is, toward the cover member 240. In thismanner, it is possible to emit the fluorescent light 165 in an identicaldirection from the phosphor optical element 100, without increasing thelight-emitting area of the fluorescent light 165. In other words, thelight-emitting area of the fluorescent light 165 can be reduced withoutreducing the area of the phosphor-containing member 30.

Note that, the incident light 163 having the wavelength of 450 nm isscattered by the phosphor particles 132 and propagates in a lateraldirection. However, the laterally propagated light is absorbed by thephosphor particles 132 in the vicinity of incident position andconverted into fluorescent. Thus, the light-emitting area does notincrease.

Next, a method of manufacturing the phosphor optical element 100according to this embodiment is described using FIG. 9. FIG. 9 is across-sectional view for describing processes in a method ofmanufacturing a phosphor optical element according to this embodiment.

First, as shown in (a) in FIG. 9, for example, on the transparent base10 which includes a transparent base such as glass, a transparent resinfilm, or the like, the base member 120 is formed by alternately stacking(i) the first base layer 121 that includes a film composed of a TiO₂layer and ZnO layers sandwiching the TiO₂ layer, for example, and (ii)the second base layer 122 that includes SiO₂ for example, until, forexample, nine layers are stacked. At this time, formation is performedto have the first base layer 121 including ZnO to be the topmost surfaceof the base member 120.

Subsequently, as shown in (b) in FIG. 9, on the base member 120 (thefirst base layer 121), resist 136 is formed which is patterned tocorrespond to the arrangement of the triangular lattice of thetransparent members 135 of the phosphor-containing layer 130. Note that,in this embodiment, the resist 136 includes a plurality of openings eachof which is circular in the planar view.

Subsequently, the transparent base 10 including the resist 136 formed onthe base member 120 is immersed approximately for five hours in asolution which is for forming a film of zinc oxide crystal and includeszinc nitrate hexahydrate and hexamethylene tetramine heated to 70degrees Celsius. With this, the columnar transparent member 135including ZnO is formed as shown in (c) in FIG. 9.

More specifically, 0.1M zinc nitrate hexahydrate (manufactured by WakoPure Chemical Industries, Ltd., Wako special grade) and 0.1Mhexamethylene tetramine (manufactured by Wako Pure Chemical Industries,Ltd., special grade reagent) are dissolved in pure water and adjusted toprepare solution for forming a film of zinc oxide crystal. The solutiontemperature of the adjusted solution is set to 70 degrees Celsius, andthe above-described transparent base 10 is immersed in the solution.With this, for example, ZnO crystal of 500 nm grows on the base member120 (the first base layer 121) exposed in the opening of the patternedresist 136. After this, the transparent base 10 is removed from thesolution, cleaned with pure water, and dried.

Next, as shown in (d) in FIG. 9, the resist 136 is removed. With this,the transparent members 135 that are cylindrical standing pillarsforming a triangular lattice are formed on the base member 120.

Next, as shown in (e) in FIG. 9, from above the transparent members 135that are arranged in a triangular lattice, a phosphor-containing resinmaterial is dropped which is obtained by adding the phosphor particles132 that are, for example, InP/ZnS core shell quantum dot phosphors tothe transparent member 131 including, for example, a silicone resin.After this, the above is kept in a vacuum. With this, thephosphor-containing resin material including the phosphor particles 132is filled in a space between the transparent members 135.

Next, as shown in (f) in FIG. 9, the cover member 240, which includesglass for example, is pressed by applying pressure from above thetransparent member 135. With this, it is possible to form thephosphor-containing layer 130 which includes: the phosphor-containingmember 133 including the transparent member 131 that includes thephosphor particles 132; and the transparent member 135. In this manner,the phosphor optical element 100 according to this embodiment can beeasily manufactured.

Next, a phosphor optical element 100A according to Modification 1 ofEmbodiment 2 of the present disclosure is described using FIG. 10. FIG.10 is a cross-sectional view showing a configuration of a phosphoroptical element according to Modification 1 of Embodiment 2 of thepresent disclosure. Note that, a configuration of the phosphor opticalelement 100A according to this modification is substantially the same asthe configuration of the phosphor optical element 100 according toEmbodiment 2. Thus, this modification mainly describes portions that aredifferent from Embodiment 2. Note that, in FIG. 10, the same structuralelements as those in FIG. 6A are denoted with the same reference signs.

As shown in FIG. 10, the phosphor optical element 100A according to thismodification is different in a configuration of a cover member whencompared with the phosphor optical element 100 according to Embodiment 2shown in FIG. 6A.

More specifically, a cover member 140 in this modification is adielectric multilayer film which includes (i) a first cover layer 141including, for example, ZnO/TiO₂/ZnO, that is, for example, a fourthrefractive index layer 141 b including TiO₂ is between third refractiveindex layers 141 a including ZnO, and (ii) a second cover layer 142 thatincludes, for example, SiO₂. Note that, the first cover layer 141 andthe second cover layer 142 are alternately stacked in a directionperpendicular to the main surface of the transparent base 10.

Furthermore, in contrast to the base member 120, the cover member 140acts as a mirror to a wavelength of the incident light (excitationlight) from the excitation light source, and is transparent to awavelength of the fluorescent light emitted from the phosphor-containinglayer 130. More specifically, the cover member 140 functions as a seconddichroic mirror which reflects the excitation light and transmits thefluorescent light from the phosphor-containing layer 130.

With the phosphor optical element 100A according to this modification,the advantageous effect due to the two-dimensional periodic structure ofthe phosphor-containing layer 130 is produced, and an advantageouseffect of holding the phosphor-containing layer 130 between dichroicmirrors of the base member 120 including a dielectric multilayer filmand the cover member 140 is produced as described in Embodiment 1. Morespecifically, compared to the phosphor optical element 100 according toEmbodiment 2, the phosphor optical element 100A according to thismodification can (i) efficiently generate fluorescent light in thephosphor-containing layer 130 because the incident light passes throughthe base member 120 and is reflected by the cover member 140, and (ii)efficiently emit the generated fluorescent light to outside of thephosphor optical element 100A because the fluorescent light generated inthe phosphor-containing layer 130 passes through the cover member 140and is reflected by the base member 120.

Next, a phosphor optical element 100B according to Modification 2 ofEmbodiment 2 of the present disclosure is described using FIG. 11. FIG.11 is a cross-sectional view showing a configuration of a phosphoroptical element according to Modification 2 of Embodiment 2 of thepresent disclosure. Note that, the phosphor optical element 100Baccording to this modification has a configuration substantially thesame as the configuration of the phosphor optical element 100 accordingto Embodiment 2. Thus, this modification mainly describes portions whichare different from Embodiment 2. Note that, in FIG. 11, the samestructural elements as those in FIG. 6A are denoted with the samereference signs.

As shown in FIG. 11, compared to the phosphor optical element 100according to Embodiment 2 shown in FIG. 6A, the phosphor optical element100B according to this modification is different in the configuration ofthe columnar transparent member.

Specifically, a transparent member 135B according to this modificationis configured to have a conic trapezoidal shape so as to have a taperedstructure in which the area of the cross-section gradually decreasesfrom the transparent base 10 side (the base member 120 side) toward thesurface side (the cover member 140 side) that is the light emissionside.

With this configuration, in the phosphor optical element 100B accordingto this modification, the ratio of the phosphor-containing member 133 tothe phosphor-containing layer 130 can be changed in a travelingdirection of the incident light. With this, the fluorescent lightconversion efficiency in the phosphor particles 132 can be improved, andthe fluorescent light emitted from the phosphor particles 132 can bereflected by the side surface of the transparent member 135B and guidedto the emission side of the phosphor optical element 100B. Thus, thefluorescent light generated in the phosphor-containing layer 130 can beefficiently emitted to the outside of the phosphor optical element 100B.

Next, a phosphor optical element 100C according to Modification 3 ofEmbodiment 2 of the present disclosure is described using FIG. 12A andFIG. 12B. FIG. 12A is a cross-sectional view showing a configuration ofa phosphor optical element according to Modification 3 of Embodiment 2of the present disclosure. FIG. 12B is a cross-sectional view showing aconfiguration of the phosphor optical element according to Modification3 of Embodiment 2 of the present disclosure, taken along a line A-A ofFIG. 12A. Note that, in FIG. 12A and FIG. 12B, the same structuralelements as those in FIG. 6A and FIG. 6B are denoted by the samereference signs.

As shown in FIG. 12A and FIG. 12B, a phosphor optical element 100Caccording to this modification has a configuration obtained by swappingthe phosphor-containing member 133 and the transparent member 135 in thephosphor-containing layer 130 in the phosphor optical element 100 shownin FIG. 6A and FIG. 6B.

More specifically, in a phosphor-containing layer 130C in thismodification, each of the phosphor-containing members 133 is acylindrical rod, and is disposed to form a triangular lattice.Furthermore, the transparent member 135 is formed to fill the spacebetween the phosphor-containing members 133.

With the configuration of the phosphor optical element 100C according tothis modification as well, a similar advantageous effect can be producedas the phosphor optical element 100 according to Embodiment 2. Morespecifically, configurations of the phosphor-containing member 133 andthe transparent member 135 can be freely changed according to the designof the two-dimensional periodic structure.

Subsequently, a configuration and operations of a light-emitting device199 using a phosphor optical element according to this embodiment isdescribed using FIG. 13. FIG. 13 is a diagram for describing aconfiguration and operations of a light-emitting device using thephosphor optical element according to Embodiment 2 of the presentdisclosure.

As shown in FIG. 13, the light-emitting device 199 according to thisembodiment includes a package 151 including a recess, a light-emittingelement 150 mounted on the base of the recess, and the phosphor opticalelement 100 formed above the package 151. The optical axis of thelight-emitting element 150 is perpendicular to the surface of thetransparent base 10 of the phosphor optical element 100. The followingdescribes structural elements of the light-emitting device 199.

The package 151 includes, for example, a white resin, and an innersurface of the recess is a reflecting surface tilted to reflect thelight emitted by the light-emitting element 150 toward the lightextraction direction (the phosphor optical element 100 side). Note that,the inside of the recess of the package 151 may be filled with atransparent resin in which diffusing materials are dispersed.

The light-emitting element 150 is the excitation light source for thephosphor optical element 100, and is a semiconductor light-emittingelement, such as a light-emitting diode (LED) which emits, for example,ultraviolet light to blue light having an emission wavelength of 350 nmto 500 nm. The light-emitting element 150 in this embodiment uses an LEDchip having an emission wavelength of 450 nm. Note that, thelight-emitting element 150 mounted on the base of the recess of thepackage 151 is electrically connected to a lead frame (not shown)embedded in the base of the recess of the package 151.

The phosphor optical element 100 is disposed on the upper surface of thepackage 151 with a predetermined distance from the light-emittingelement 150. In this embodiment, the phosphor optical element 100 isformed to cover the opening of the recess of the package 151. Note that,a collimating lens 158 is disposed on the light emission side of thelight-emitting device 199.

With the light-emitting device 199 having the above-describedconfiguration, the incident light 163 (excitation light) emitted fromthe light-emitting element 150 enters the phosphor optical element 100,and is converted into the fluorescent light 165. The fluorescent light165 is emitted from the phosphor optical element 100 with a lightdistribution angle narrower than the incident light 163 of apredetermined Lambertian distribution emitted from the light-emittingelement 150, and is converted into parallel light 167 by the collimatinglens 158. At this time, the fluorescent light 165 is emitted from asmall light-emitting area about the same size as the light-emittingelement 150. Thus, good parallel light having a small oblique lightcomponent can be obtained with the collimating lens 158.

Although the phosphor optical element and the light-emitting deviceaccording to Embodiment 2 have been described thus far, the presentdisclosure is not limited to the above-described embodiments ormodifications.

For example, although a light-emitting diode is used as thelight-emitting element 150 in the light-emitting device 199 according tothis embodiment, a semiconductor laser or a super luminescent diode eachof which is a light-emitting element of an end-face emission type inwhich an optical waveguide is formed may be used. In this case, theemission light of the light-emitting element is emitted parallel to thebase of the recess. Thus, for example, the emitted light may be guidedin a perpendicular direction using the tilted side face of the package.Furthermore, although the light-emitting element 150 has the emissionwavelength of 450 nm, a semiconductor laser or the like which emitslight having a wavelength from 380 nm to 440 nm may be used, forexample.

Furthermore, the phosphor particle 132 of the phosphor-containing member133 in the phosphor optical elements 100, 100A, 1006, and 100C accordingto this embodiment is the InP/ZnS core shell quantum dot phosphor, butis not limited thereto. As the material of the quantum dot phosphor, forexample, at least one selected from InN, InP, InAs, InSb, GaN, GaP,GaAs, GaSb, AlN, AlP, AlAs, AlSb, and BN that are Group II-V compoundsemiconductors, at least one selected from HgS, HgSe, HgTe, CdS, CdSe,CdTe, ZnS, ZnSe, and ZnTe that are Group II-VI compound semiconductors,or at least one selected from the group consisting of mixed crystal ofthe above can be used.

Furthermore, although the phosphor particle 132 in this embodiment is anondoped quantum dot phosphor, a doped quantum dot phosphor may be used.As the material included in the doped quantum dot phosphor, for example,at least one from ZnS:Mn²⁺, CdS:Mn²⁺, and YVO₄:Eu³⁺ can be used.Furthermore, in a broader sense, it is sufficient that the phosphorparticle 132 be a phosphor particle which (i) has a size no greater thanthe wavelength of the fluorescent light and, (ii) is a phosphor particlehaving a reduced non-light emission recombination loss caused by surfaceflaws. For example, YAG:Ce nanoparticles may be used.

Furthermore, the resin material of the transparent member 131 in thisembodiment is a silicone resin, but is not limited thereto. As the resinmaterial of the transparent member 131, other than the silicone resin, atransparent resin material, such as an acrylic resin or an epoxy resin,can be used. Furthermore, the transparent member 131 need not include aresin material, and may include, for example, an inorganic transparentmaterial, such as low melting point glass. In this case, thephosphor-containing member 133 may be configured by mixing the phosphorparticle 132 having a size no greater than a wavelength of thefluorescent light into the inorganic transparent material.

Furthermore, the first base layer 121, the second base layer 122, thefirst cover layer 141, and the second cover layer 142 in this embodimentis a multilayer film including a combination of TiO₂, ZnO, and SiO₂, butis not limited thereto. For example, the base member 120 and the covermember 140 may be a dielectric multilayer film including a lowrefractive index material and a high refractive index material. As thematerial having a low refractive index, for example, one of Bi₂O₃,Ta₂O₅, La₂O₃, Al₂O₃, SiO_(x) (x≦1), LaF₃, a complex oxide of La₂O₃ andAl₂O₃, and a complex oxide of Pr₂O₃ and Al₂O₃, or an complex oxide of atleast two materials selected from the above, or a dielectric materialsuch as a fluoride or the like, such as CaF₂, MgF₂, or LiF can be used.Furthermore, as a material having a high refractive index, for example,(i) one of TiO₂, Nb₂O₅, and Ta₂O₅ or (ii) a complex oxide or the likeincluding as a main component one of TiO₂, Nb₂O₅, and Ta₂O₅ can be used.

Although the phosphor optical element and the light-emitting deviceaccording to the present disclosure have been thus far described basedon the embodiments and modifications, the present disclosure is notlimited to the above-described embodiments and modifications. Variousmodifications that may be conceived by those skilled in the art which donot depart from the essence of the present disclosure are intended to beincluded within the scope of the present disclosure. Furthermore,respective structural elements of different embodiments may bearbitrarily combined within the scope of the essence of the presentdisclosure.

INDUSTRIAL APPLICABILITY

A phosphor optical element and a light-emitting device according to thepresent disclosure is useful as a light source of backlight in a liquidcrystal television, a liquid crystal monitor, or the like or a lightsource of a projection-type display, such as a projector.

The invention claimed is:
 1. A phosphor optical element comprising: abase member; a phosphor-containing member that includes a transparentmember containing a phosphor particle; and a cover member, wherein thebase member, the phosphor-containing member, and the cover member aresequentially formed on a transparent base that is transparent to awavelength of incident light from an excitation light source, the basemember is a dielectric multilayer film whose layers are stacked in adirection perpendicular to the transparent base, the phosphor-containingmember is in direct contact with the dielectric multilayer film, thephosphor particle has a diameter no greater than the wavelength of theincident light, and in an arbitrary cross section of thephosphor-containing member in a direction perpendicular to a mainsurface of the transparent base, the phosphor-containing member has, inat least one of (i) a direction perpendicular to and (ii) a directionhorizontal to the main surface of the transparent base, a thickness nogreater than the wavelength of the incident light.
 2. The phosphoroptical element according to claim 1, wherein the cover member includesa multilayer film whose layers are stacked in a direction perpendicularto the transparent base.
 3. The phosphor optical element according toclaim 2, wherein the multilayer film is a dielectric multilayer film. 4.The phosphor optical element according to claim 1, wherein the basemember transmits the incident light and reflects fluorescent lightemitted from the phosphor-containing member.
 5. The phosphor opticalelement according to claim 1, wherein the phosphor-containing memberhas, in a two dimensional planar direction that is a direction parallelto the main surface of the transparent base, a refractive indexdistribution according to a two-dimensional periodic structure.
 6. Thephosphor optical element according to claim 5, wherein thetwo-dimensional periodic structure includes a photonic crystal.
 7. Thephosphor optical element according to claim 1, wherein thephosphor-containing member includes two types of transparent materialshaving different refractive indices, and the phosphor particle isincluded in at least one of the two types of transparent materialshaving different refractive indices.
 8. The phosphor optical elementaccording to claim 7, wherein at least one of the two types oftransparent materials having different refractive indices includes ZnO.9. The phosphor optical element according to claim 1, wherein a topmostlayer of the base member is a ZnO film.
 10. The phosphor optical elementaccording to claim 1, wherein the phosphor-containing member includes afirst phosphor-containing member, a second phosphor-containing member,and a transparent member disposed between the first phosphor-containingmember and the second phosphor-containing member.
 11. A light-emittingdevice comprising: a light-emitting element that is an excitation lightsource; and a phosphor optical element including a transparent base thatis transparent to a wavelength of incident light from the excitationlight source, wherein the light-emitting element has an optical axisperpendicular to a surface of the transparent base of the phosphoroptical element, the phosphor optical element further includes: a basemember; a phosphor-containing member that includes a transparent membercontaining a phosphor particle; and a cover member, the base member, thephosphor-containing member, and the cover member are sequentially formedon the transparent base, the base member is a dielectric multilayer filmwhose layers are stacked in a direction perpendicular to the transparentbase, the phosphor-containing member is in direct contact with thedielectric multilayer film, the phosphor particle has a diameter nogreater than the wavelength of the incident light, and in an arbitrarycross section of the phosphor-containing member in a directionperpendicular to a main surface of the transparent base, thephosphor-containing member has, in at least one of (i) a directionperpendicular to and (ii) a direction horizontal to the main surface ofthe transparent base, a thickness no greater than the wavelength of theincident light.
 12. The phosphor optical element according to claim 11,wherein the cover member includes a multilayer film whose layers arestacked in a direction perpendicular to the transparent base.
 13. Thephosphor optical element according to claim 12, wherein the multilayerfilm is a dielectric multilayer film.
 14. The phosphor optical elementaccording to claim 11, wherein the base member transmits the incidentlight and reflects fluorescent light emitted from thephosphor-containing member.
 15. The phosphor optical element accordingto claim 11, wherein the phosphor-containing member has, in a twodimensional planar direction that is a direction parallel to the mainsurface of the transparent base, a refractive index distributionaccording to a two-dimensional periodic structure.
 16. The phosphoroptical element according to claim 15, wherein the two-dimensionalperiodic structure includes a photonic crystal.
 17. The phosphor opticalelement according to claim 11, wherein the phosphor-containing memberincludes two types of transparent materials having different refractiveindices, and the phosphor particle is included in at least one of thetwo types of transparent materials having different refractive indices.18. The phosphor optical element according to claim 17, wherein at leastone of the two types of transparent materials having differentrefractive indices includes ZnO.
 19. The phosphor optical elementaccording to claim 11, wherein a topmost layer of the base member is aZnO film.
 20. The phosphor optical element according to claim 11,wherein the phosphor-containing member includes a firstphosphor-containing member, a second phosphor-containing member, and atransparent member disposed between the first phosphor-containing memberand the second phosphor-containing member.